Sudoku Naked Pair Method

The Naked Pair method is a more advanced method that can be used when other methods cannot solve the puzzle. This may be required for medium difficulty puzzles. This method is also known as the Disjoint Subset method.

In both of these examples, look at the cells marked with green. Notice how the numbers 1 and 7 are both the only possibilities. These are a naked pair. Since 1 and 7 must occur in these two cells, we can eliminate 1 and 7 from the cells marked with red.

A Naked Pair can become a Hidden Pair if there are extra possible values for those cell. In this third example on the left, the cells marked with green make a Hidden Pair with the numbers 1 and 7. We can safely remove 3 and 8 as candidates for the green cells because we know that they must contain either 1 or 7.